One of the most critical applications of carbon and graphite is as an electrode for arc melting of steel. During the past 20 years the use of electric furnaces for melting steel has grown from a small volume specialty process to a high volume process with probably the lowest production costs of any of the recognized metallurgical processes. The process typically consumes from 10-12 pounds of electrode material for each ton of steel produced for about 8% of the total production cost.
During operation of electric arc steel furnaces, the electrodes are subject to mechanical, chemical and electrical stresses of such severity that, particularly for ultra high powered furnaces, only graphite of very high quality can be used. The electrodes are subject to the mechanical stresses from falling scrap being melted and from the degree of inductance caused by the high AC current, and are particularly subject to oxidation due to the temperature reached, which may range up to the sublimation temperature of about 3600.degree. C.
Pure graphite is one of the more inert and least reactive materials known at high temperatures. However, oxidation is a highly significant cause of deterioration of column strength of graphite electrodes in arc furnaces, and results in loss of electrode material. Thus retardation of the oxidation reactions could be highly beneficial in lowering consumption both by direct oxidation and by lessening breakage caused by oxidation-induced loss of strength.
During operation of an electric arc furnace, normally three electrodes are used, each of which is connected to one phase of the power supply through a metal clamp, and as the electrode is consumed, additional sections are added at the top and the column lowered to the operating level in the furnace. Although it is generally found that oxidation retardants are ineffective above about 1200.degree. C., any improvement, even at lower temperatures, is welcome and can significantly reduce electrode consumption.